Elsevier

Clinical Biomechanics

Volume 22, Issue 1, January 2007, Pages 88-92
Clinical Biomechanics

Measurement of the tensile strength of the ventral abdominal wall in comparison with scar tissue

https://doi.org/10.1016/j.clinbiomech.2006.06.002Get rights and content

Abstract

Background. Paramedian laparotomies lead to incisional hernias in approximately 30% of cases. In contrast, incisional hernias occur very rarely in the linea alba or the ventral abdominal wall. In this setting we investigated the difference between scar tissue and the non-incised abdominal wall tissue.

Methods. At the post mortem examination of 66 recently deceased individuals, accurately measured pieces of resected tissue from the linea alba, the anterior and the posterior rectus sheath, and scar tissue following median laparotomy, were exposed to tensile loads.

Findings. In the epigastric region the tissue ruptured at a mean horizontal load of 10.0 (SD 3.4) N/mm2 in the linea alba and 6.9 (SD 2.5) N/mm2 in scar tissue (P < 0.001), and at a mean vertical load of 4.5 (SD 2.0) N/mm2 in the linea alba and 3.3 (SD 1.6) N/mm2 in scar tissue (P < 0.05). In the hypogastric region as well, scar tissue was significantly less resistant in the main direction of load.

Interpretation. Scar tissue has a significantly lesser loading capacity than the intact ventral abdominal wall and therefore poses a permanent risk for herniation. For this reason, closure of the abdominal wall should be given due consideration and subjected to further investigation. Specifically, sustained reinforcement of scar tissue by means of suture techniques or non-absorbable sutures warrants further study. When constructing meshes for reinforcement of incisional hernias, the two-fold tensile load on the midline in horizontal direction as opposed to the craniocaudal direction must be taken into account.

Introduction

The problem of incisional hernia is an extensively discussed and highly debated subject. Occurring at a rate of 11–15% in the first postoperative year, it is a poorly controlled complication of primary abdominal wall closure (Wissing et al., 1987). According to Mudge and Hughes (1985), the high initial incidence of incisional hernia is doubled in the following nine years. It may be assumed that nearly every third abdominal wall closure is unable to resist loads and culminates in tissue rupture.

Scars constitute a weak site of the abdominal wall. Therefore, it is important to identify the differences between this tissue and the load-bearing, tear-resistant linea alba. Furthermore, correction of incisional hernia is associated with high recurrence rates of up to 24% despite the widespread use of mesh as reinforcement (Cassar and Munro, 2002, Flum et al., 2003, Luijendijk et al., 2000, Rios et al., 2001). The suture technique and the mesh material are primarily selected by the surgeon, based on his own experience, published reports of other surgeons, and the results of evidence-based medicine.

No attempts have been made so far to compare loads and the load-bearing strength of the linea alba and scar tissue in order to draw conclusions about closure of the abdominal wall or the treatment of incisional hernias.

The interaction between the muscles of the abdominal wall and their effect on the linea alba and scar tissue result from the load-bearing capacity of these structures in various directions of stress. The purpose of the present study was to compare the stress resistance of the linea alba and of scar tissue, and to provide evidence of the poor tensile strength of scar tissue. The results of the investigation led to significant conclusions about primary abdominal wall closure and the treatment of incisional hernias.

Section snippets

Methods

In 66 recently deceased patients with an average age of 77 years (range: 17–94 years), tensile load tests on the ventral abdominal wall were performed in the course of post mortem investigations within 24 h after death. The linea alba was subjected to horizontal and vertical tensile load in the epigastrium and the hypogastrium. In cases of pre-existing median laparotomies, which had been performed on average 12 years previously (range: 0.5–41 years), the scar tissue was subjected to tensile loads in

Results

Of the 66 recently deceased persons, 27 had a median laparotomy scar while 39 had an intact linea alba. Thirty-six female and 30 male cadavers aged on average 77 years (range: 17–94 years) were investigated. Of these, three cadavers were less than 50 years of age (17, 39, 48 years) and 7 cadavers were between 50 and 60 years of age. All others were older than 60 years. The stability of the linea alba in the epigastrium during horizontal tensile load was significantly superior (mean 10.0, SD 3.4 N/mm2)

Scar tissue

In the present study we found that the load-bearing capacity of scar tissue is approximately 30% less than that of the linea alba in nearly all directions; the maximum difference was 3 N/mm2 in horizontal direction in the epigastrium. We were thus able to obtain a quantitative measure of the strength of scar tissue compared to that of the linea alba. This provides an approximate value of the stability required for the treatment of incisional hernia. Furthermore, we found that this low resistance

Conclusion

It may be concluded that scar tissue is unstable in terms of its stress resistance and therefore poses a high risk of hernia for patients with median laparotomies. The fact that the horizontal load on the linea alba is twice as high as the vertical load should be taken into account during primary abdominal wall closure and also during mesh construction. This field calls for extensive research in the future.

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